Has an AFL game ever ended 73-20?
Exactly once. On June 26, 1897, Sydney beat Melbourne 73-20, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 73-20 in league history.
That makes 73-20 the 3884th most common final score out of 6,649 that have ever occurred in AFL. One point away, 74-20 has happened never and 73-21 has happened 1 times.